This invention relates generally to a method and apparatus for jetting liquid metal, and ore specifically to a continuous mode solder jetting system and method.
Various soldering schemes have been developed for electrically bonding semiconductor integrated circuit (IC) chips to a substrate (e.g., a printed circuit board). In some schemes, a semiconductor IC chip is bonded to a substrate by applying a small solder bump to the bottom surface of the chip, aligning the solder bump with a bond pad on the surface of the substrate, and heating the solder bump until it reflows. In some other schemes, solder bumps are applied to bonding pads on a substrate; afterwards, electronic components are bonded to the substrate by positioning the components over the solder bumps and by heating and reflowing the solder bumps. In some schemes IC chips are bonded to a patterned layer of solder created by applying a thin layer of solder paste to a substrate through holes in a stencil, leaving a selected solder pattern on the substrate. Recently, solder jet systems have been proposed for depositing molten solder droplets onto a substrate in a selected pattern. Such systems include a solder droplet ejector, which may eject solder droplets on-demand or continuously.